Deposition processes, including chemical vapor deposition (CVD) processes, are commonly used in the manufacturing of semiconductor devices. For example, in a typical CVD process, reactant gases are introduced into a reaction chamber and directed to a heated substrate to induce controlled chemical reactions, which result in the deposition of a thin film on the surface of the substrate. During the deposition process, chamber pressure is precisely controlled by one or more mechanical devices, such as vacuum valves, connected downstream from the reaction chamber. For example, an isolation valve is typically connected directly to the exhaust gas port of the reaction chamber, a throttle valve is situated downstream from the isolation valve, and a vacuum pump is located further downstream from both of the isolation and throttle valves. The plumbing between the reaction chamber and the vacuum pump (e.g., the pipelines and valves) is generally referred to as a foreline, a roughing line or a vacuum pumping line.
During a deposition, process, the throttle valve can cycle between open and closed positions to regulate the gas pressure inside of the reaction chamber. Most of the material produced from the reactant gases is deposited on the substrate surface in the reaction chamber. However, some material is also deposited on surfaces outside of the reaction chamber, such as on the throttle valve. As unwanted material accumulates on the throttle valve, the throttle valve's useful life can be reduced by, for example, introduction of seal wear, load addition, requirement for high torque drive systems, and alteration of conductance characteristics. Ultimately, unwanted material deposits on a throttle valve diminish the precise operation of the valve, thereby reducing the valve's ability to control gas pressure inside of the reaction chamber. Other vacuum valves along the vacuum pumping line can be similarly affected by unwanted material deposition. In addition, the position of a throttle valve during closed loop pressure control can provide useful diagnostic information. However, because valve position varies with quantity of deposition, unwanted deposition on a valve can limit the usefulness of valve positioning as an indication of other changes in the system.
Typically, an operator needs to manually remove valves in a mechanical system for cleaning or replacement. This requires downtime of the tool and venting of the foreline plumbing. Alternatively, remote plasma sources have been used for pump and foreline cleaning, where the plasma output is directed at the foreline, but not so close to the valves as to provide optimized and targeted component cleaning.
Further, during a wafer deposition process, unwanted material produced from the reactant gases can also be deposited along the vacuum pumping line as the reactant gases are pumped out from the processing chamber through the pumping line. Similar to the throttle valve, accumulation of the unwanted material in the vacuum pumping line can produce a host of problems, including clogging the pumping line and other downstream equipment, interfering with normal operation of the associated vacuum pump, reducing the vacuum pump's useful life, and contaminating processing steps in the processing chamber.